ci: Add GitHub Actions workflow to run the test suite

.github/workflows/test.yaml

@@ -0,0 +1,19 @@
+---
+name: test
+
+on:
+- push
+- pull_request
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v4
+    - name: Install uv
+      uses: astral-sh/setup-uv@v6
+      with:
+        python-version-file: .python-version
+    - name: Run tests
+      run: uv run pytest

CLAUDE.md

@@ -47,8 +47,24 @@ current configuration and takes no arguments.
   markers (`:white_check_mark:` success, `:cross_mark:`/`:boom:` failure).
 - SSL warnings are silenced at import via
   `urllib3.disable_warnings(urllib3.exceptions.InsecureRequestWarning)`.
-- No test suite, linter config, or build step exists. The README advertises
-  `black` code style; new code should match it.
+- No linter config or build step exists. The README advertises `black` code
+  style; new code should match it. See *Testing* below for the test suite.
+
+## Testing
+
+A `pytest` suite lives in `tests/`, with `pytest` declared in the `dev`
+dependency group in `pyproject.toml`. Run it with:
+
+```bash
+uv run pytest
+```
+
+Tests cover the pure, side-effect-free helpers within tools. Because tools are
+hyphenated standalone scripts (e.g. `load-er.py`) rather than importable
+modules, tests load them by path via `importlib` — see
+`tests/test_load_er.py`. Extract logic into such helpers so it can be tested
+without live Squonk2 API calls. GitHub Actions runs the suite on every push and
+pull request (`.github/workflows/test.yaml`).
 
 ## Standard tool structure
 

README.md

@@ -2,6 +2,8 @@
 
 ![GitHub tag (latest SemVer)](https://img.shields.io/github/v/tag/informaticsmatters/squonk2-python-cl-tools)
 
+[![test](https://github.com/InformaticsMatters/squonk2-python-cl-tools/actions/workflows/test.yaml/badge.svg)](https://github.com/InformaticsMatters/squonk2-python-cl-tools/actions/workflows/test.yaml)
+
 [![Code style: black](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/psf/black)
 
 A collection of Python-based Command line tools to help manage and maintain